Circulatory system

Simplified diagram of the human Circulatory system in anterior view.

The circulatory system, also known as the cardiovascular system, blood-vascular system, or simply circulatory, is an essential system in the human body responsible for the transport of blood, nutrients, oxygen, and waste products. It comprises the heart, a robust muscular pump, and a network of vessels - arteries, veins, and capillaries. This closed circuit ensures that blood is continuously recirculated, maintaining homeostasis and facilitating cellular function.

Structure

• Heart: Serving as the central pumping mechanism, the heart ensures the movement of blood throughout the body.
• Arteries: These are robust, elastic vessels that transport blood away from the heart.
• Veins: Vessels responsible for carrying blood back to the heart.
• Capillaries: The tiniest of blood vessels, capillaries facilitate the exchange of nutrients, oxygen, and waste products between the blood and body tissues.

Development

The circulatory system is among the first to develop in a growing embryo, underlining its critical role. By the fourth week following fertilization, the primitive heart begins its rhythmic beating, well before many other major organ systems.

Functions

• Transport: At the core of its responsibilities, the circulatory system ensures the distribution of oxygen, nutrients, hormones, and other essential substances to cells and tissues.
• Waste Removal: The system aids in the removal of waste products, including carbon dioxide and metabolic byproducts, facilitating their excretion.
• Homeostasis Maintenance: By regulating the flow and distribution of blood, the circulatory system helps maintain a constant internal environment, ensuring cells receive necessary resources and waste products are efficiently removed.

Microscopic Functions

At the capillary level, blood achieves its ultimate purpose in transport. Through the thin walls of the capillaries, essential nutrients and oxygen are delivered to surrounding cellular fluids, while waste products are concurrently removed.

Regulation and Control

The circulatory system doesn't operate in isolation but is influenced by numerous control mechanisms that regulate and integrate its diverse functions. This coordination ensures specific body regions receive blood as per their requirements. Whether there's an increased demand for nutrients in a particular area or heightened waste production in another, these mechanisms maintain a stable environment around each cell.

Glossary of Circulatory System Terms

• Aortic orifice – The opening from the left ventricle into the aorta, guarded by the aortic valve, through which oxygenated blood is ejected during systole.

• Basilic vein – A large superficial vein of the upper limb that drains parts of the hand and forearm, eventually joining the brachial vein to form the axillary vein.

• Blood–brain barrier – A selective permeability barrier formed by endothelial cells of cerebral capillaries, protecting the central nervous system from pathogens and toxins while regulating the passage of essential substances.

• Blood–spinal cord barrier – Similar to the blood–brain barrier, this barrier controls the environment of the spinal cord, formed by endothelial tight junctions in the spinal microvasculature.

• Cardiovascular physiology – The study of the functions and mechanisms of the heart and blood vessels, including topics such as cardiac output, blood pressure, vascular resistance, and hemodynamics.

• Cephalic vein – A superficial vein of the upper arm that runs along the lateral side and drains into the axillary vein, commonly used for venous access in medical procedures.

• Circulatory system of gastropods – Refers to the open circulatory system in gastropods, such as snails and slugs, in which hemolymph is pumped through open cavities rather than closed vessels.

• Circulatory system of the horse – The highly efficient closed circulatory system of horses, adapted for high-performance activity and including a large heart, extensive vascular networks, and muscular adaptations for venous return.

• Endothelial activation – A process by which endothelial cells respond to inflammatory signals, leading to the expression of adhesion molecules and cytokines, playing a crucial role in immune responses and atherosclerosis.

• Humoral factor – A substance, often a hormone or cytokine, circulating in the blood that regulates vascular tone, cardiac function, or immune system responses.

• Microcirculation – The part of the circulatory system composed of arterioles, capillaries, and venules, responsible for the exchange of nutrients, gases, and waste between blood and tissues.

• Mueller–Weiss syndrome – A rare degenerative disorder of the navicular bone in the foot, sometimes associated with compromised peripheral circulation and systemic vascular disorders.

• Precapillary resistance – Resistance to blood flow offered by arterioles before the capillary bed, which plays a major role in regulating blood pressure and tissue perfusion.

• Precapillary sphincter – A ring of smooth muscle located at the entrance to capillaries, controlling blood flow into individual capillary beds in response to metabolic demand.

• Rete mirabile – A complex network of interconnected blood vessels found in some vertebrates, including humans (e.g., in the kidneys and testicles), involved in countercurrent exchange of heat or solutes.

• Society of Cardiovascular Computed Tomography – A professional society that promotes research, education, and clinical excellence in cardiovascular computed tomography imaging.

• Transport maximum – The maximum rate at which a solute can be transported across a membrane, such as the renal tubules or capillary endothelium, important in understanding glucose and solute transport in the kidney and circulatory system.

• Vascularity – The degree to which a tissue or organ is supplied with blood vessels; often used to describe tissues with high metabolic activity such as muscle or tumors.

• Vasomotion – The rhythmic contraction and relaxation of vascular smooth muscle, particularly in arterioles, regulating local blood flow and tissue perfusion.

• Watershed area (medical) – A region of the brain or other organ that lies at the border of two arterial supply zones, making it especially vulnerable to ischemia in cases of reduced blood flow.

See Also

• Heart
• Artery
• Vein
• Capillary
• Homeostasis

This article is a medical stub. You can help WikiMD by expanding it!
Most recent articles Ongoing trials	Wikipedia